Polarizer stack

ABSTRACT

A polarizer stack including an absorbing polarizer and a multilayer polymeric reflective polarizer bonded together is described. The absorbing polarizer has a first block axis and the reflective polarizer has a second block axis substantially parallel to the first block axis. The reflective polarizer may be substantially free of micro-wrinkling when the polarizer stack adhered to a glass layer is heated at 95° C. for 100 hours.

BACKGROUND

U.S. Pat. No. 6,025,897 (Weber et al.) describes a reflective polarizerand an absorbing polarizer bonded directly to the reflective polarizer.

SUMMARY

In some aspects of the present description, a polarizer stack includingan absorbing polarizer and a multilayer polymeric reflective polarizerbonded together is provided. The absorbing polarizer has a first blockaxis and the reflective polarizer has a second block axis substantiallyparallel to the first block axis. The reflective polarizer has ashrinkage in a range of 0.4 percent to 3 percent along the second blockaxis when the reflective polarizer is heated at 95° C. for 40 minutes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a polarizer stack;

FIG. 2 is a schematic cross-sectional view of a display including apolarizer stack;

FIG. 3 is a schematic cross-sectional view of a portion of a multilayerreflective polarizer exhibiting micro-wrinkling;

FIG. 4 is a plot of shrinkage of various polarizers along the block axisversus time;

FIG. 5 is a plot of shrinkage of various polarizers along the pass axisversus time; and

FIG. 6 is a bar graph of roughness for various polarizers held atvarious temperatures for 1000 hours.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings that forms a part hereof and in which various embodiments areshown by way of illustration. The drawings are not necessarily to scale.It is to be understood that other embodiments are contemplated and maybe made without departing from the scope or spirit of the presentdisclosure. The following detailed description, therefore, is not to betaken in a limiting sense.

A polarizer stack that includes both a reflective polarizer and anabsorbing polarizer is sometimes used in display applications. Forexample, the inner polarizer (the polarizer facing away from the viewer)in a liquid crystal display (LCD) may include a reflective polarizerfacing the backlight and an absorbing polarizer facing the displaypanel. The outer polarizer (the polarizer facing the viewer) in a liquidcrystal display (LCD) typically includes just an absorbing polarizer andoptionally a compensation film on the backlight side of that absorbingpolarizer. Polarizer stacks and their use in display applications aregenerally described in U.S. Pat. No. 6,025,897 (Weber et al.) which ishereby incorporated by reference herein to the extent that it does notcontradict the present description.

The reflective polarizer may be a polymeric multilayer reflectivepolarizer which includes a plurality of alternating polymeric layers.Such polymeric multilayer reflective polarizers are generally describedin U.S. Pat. Nos. 5,882,774 (Jonza et al.); 5,962,114 (Jonza et al.);5,965,247 (Jonza et. al.); 6,939,499 (Merrill et al.); 6,916,440(Jackson et al.); 6,949,212 (Merrill et al.); and 6,936,209 (Jackson etal.); for example, each of which is hereby incorporated by referenceherein to the extent that it does not contradict the presentdescription. In brief summary, a polymeric multilayer reflectivepolarizer can be made by coextruding a plurality of alternatingpolymeric layers (e.g., hundreds of layers), uniaxially or substantiallyuniaxially stretching the extruded film (e.g., in a linear or parabolictenter) to orient the film, and optionally applying a heat set to theoriented film as described in U.S. Pat. App. Pub. No. 2013/0123459(Merrill et al.) and U.S. Pat. No. 6,827,886 (Neavin et al.), both ofwhich are hereby incorporated by reference herein to the extent thatthey do not contradict the present description. Polymeric multilayerreflective polarizers include Dual Brightness Enhancement Film (DBEF)and Advanced Polarizing Film (APF), both available from 3M Company (St.Paul, Minn.). Alternatively, the reflective polarizer may be a DiffuseReflective Polarizer Film where a non-multi-layer approach is utilizedas described in U.S. Pat. No. 5,825,543 (Ouderkirk et al.); or a fiberpolarizer film where polarizing fibers are used to make a polarizingfilm as described in U.S. Pat. No. 7,738,763 (Ouderkirk et al.).

In a polymeric multilayer reflective polarizer, the alternatingpolymeric layers may be referred to as microlayers. Conventionally,reflective polarizers have been selected to provide a minimum shrinkageunder heat so that the reflective polarizer does not shrink when used ina display. This has been motivated by the low shrinkage of the glassplates used in the display and the belief that the reflective polarizershould have a correspondingly low shrinkage. An issue with using apolarizer stack having an absorbing polarizer and a conventionalreflective polarizer in a display is the phenomena of micro-wrinklingwhich refers to a corrugation/buckling in the layers of the multi-layerfilm. Micro-wrinkling is characterized by adjacent interfaces betweenlayers or the surface layer not being parallel to each other. An exampleof micro-wrinkling is illustrated in FIG. 3 which is a schematiccross-sectional view of a portion of a multilayer reflective polarizer320. Multilayer reflective polarizer 320 includes alternating firstlayers 322 and second layers 324. The first and second layers 322 and324 are alternating polymeric layers having differing refractive indicesas is known in the art. For example, first and second layers 322 and 324may have matching or substantially matching refractive indices along thex-and z-directions and may have substantially different refractiveindices along the y-direction so that light polarized along they-direction is reflected from the reflective polarizer 320 and lightpolarized along the x-direction is transmitted through the reflectivepolarizer 320. The reflective polarizer 320 exhibits a variation in thethickness h of the microlayers along at least the y-axis. Typically, thevariation in thickness will be more pronounced along the block axis ofthe reflective polarizer than along the pass axis.

In FIG. 3, the first and second layers 322 and 325 have a thickness thatis out of phase; that is, one layer is thickest where the adjacent layeris thinnest. In other cases, the thickness variation does not exhibitthe out of phase variation illustrated in FIG. 3. More generally, in amicro-wrinkled film, adjacent interfaces (e.g., interfaces 325 and 327)between microlayers are not parallel to each other. In some cases, thevariation in the shape of the interfaces varies with vertical positionin the stack (i.e. varies in the z-direction). In some cases, the outersurfaces (air-surface interfaces) are flatter than interfaces betweenmicrolayers located closer to the center of the stack. Micro-wrinklingmanifests itself as objectionable haze or iridescence in the films, andwhen examined under a microscope at a magnification of between 50 and200 times is observed to be a permanent deformation of the opticallayers. In contrast to micro-wrinkling, macro-wrinkling refers to theoverall wrinkling of the multilayer film. As illustrated in FIG. 3, in amicro-wrinkled multilayer optical film, adjacent interfaces betweenmicrolayers are not parallel. A macro-wrinkled multilayer optical filmthat is not also micro-wrinkled, would have parallel interfaces betweenthe microlayers.

In display applications, it is often desired that no micro-wrinkling isobservable when the polarizer is held at 95° C. at 1000 hours. The longaxis direction (x-axis in FIG. 3) of micro-wrinkles for a reflectivepolarizer/absorbing polarizer laminate tested at 95° C. for 1000 hoursis typically in the pass-state direction. Shrinkage of the reflectivepolarizer in the block-state direction can be adjusted in order tofrustrate such micro-wrinkling and provide a polarizer stack suitablefor use in display applications. Micro-wrinkling is described in U.S.Pat. No. 7,468,204 (Hebrink et al.) which is hereby incorporated byreference herein to the extent that is does not contradict the presentdescription. In U.S. Pat. No. 7,468,204, micro-wrinkling in multilayeroptical film is reduced by utilizing low refractive index layers havinga glass transition temperature substantially greater than thetemperature at which the film is expected to be utilized or tested.According to the present description, polarizer stacks which exhibitsubstantially no micro-wrinkling are provided where the low index layerscan have a glass transition temperature comparable to or lower than thetemperatures expected to occur in display applications. For example, apolarizer stack may be tested at 95° C. or 100° C. to ensure that nomicro-wrinkling occurs in a display application, and in someembodiments, the low index layers have a glass transition temperatureless than 100° C., or less than 95° C., or less than 80° C., or lessthan 60° C. In some embodiments, the glass transition temperature of thelow index layer is greater than 25° C. or greater than 50° C. As usedherein, glass transition temperature refers to the glass transitiontemperature determined by differential scanning calorimetry.

In some embodiments, the absorbing polarizer utilized in the polarizerstacks of the present description is an iodine-doped polyvinyl alcohol(PVA) polarizer. Such polarizers include an oriented PVA layerimpregnated with iodine. A suitable example of such a polarizer includesthe Sanritz HLC2-5618S adhesive-backed polarizer film available fromSanritz Corporation, Tokyo, Japan. Other suitable absorbing polarizersinclude oriented polymer (such as PVA) polarizers impregnated with anorganic dye.

According to the present description, it has been found thatmicro-wrinkling can occur when the absorbing polarizer shrinks more thanthe reflective polarizer when exposed to heat and that suchmicro-wrinkling can be significantly reduced or substantially eliminatedby modifying the reflective polarizer to provide a desired range ofshrinkage under heat. The shrinkage of the absorbing polarizer occurspredominately along the block axis of the absorbing polarizer when theabsorbing polarizer contains a polymer, such as PVA, oriented along theblock axis. Without intending to be limited by theory, the mechanism ofmicro-wrinkle reduction is believed to be that the additional shrinkagein the reflective polarizer prevents the reflective polarizer from beingplaced in compression while it is at an elevated temperature. This issupported by the data on shrinkage of reflective polarizers and anabsorbing polarizer reported in the Examples which suggests that byappropriately choosing the shrinkage of the reflective polarizer apolarizer stack including the reflective polarizer and an absorbingpolarizer bonded together can be obtained where the reflective polarizeris not placed in compression in any direction in the plane of the filmwhen the polarizer stack is placed at 95° C. at 1000 hours, for example.

The modification to the reflective polarizer film that reduces oreliminates micro-wrinkling can be done by adjusting the heat set processapplied to the film after the film is oriented. The heat set can becarried out in the last zones of the tenter oven used to orient the filmas described in U.S. Pat. No. 6,827,886, previously incorporated byreference. Typically, such heat set processes are used in order toreduce or minimize the shrinkage of the film when heat is subsequentlyapplied to the film. When it is desired to minimize the subsequentshrinkage of the film, the heat set temperature may be set to thehighest possible temperature that does not result in film breakage inthe tenter and the film can be relaxed in the transverse direction inthe vicinity of the heat-set zone which decreases the tension of thefilm. Higher shrinkage can be achieved by reducing the heat settemperature, by reducing the duration of the heat set treatment for agiven heat set temperature, by eliminating the heat set step, and/orreducing the relaxation of the film in the block direction. In someembodiments, in order to provide a desired shrinkage of the reflectivepolarizer for the polarizer stacks of the present description, a heatset step is applied with a reduced temperature selected to give thedesired shrinkage and/or the relaxation of the film in the blockdirection is reduced. According to the present description, it has beenfound that the desired shrinkage of the reflective polarizer in thepolarizer stack, is typically in a range of 0.4 percent to 3 percentalong the block axis of the reflective polarizer when the reflectivepolarizer is heated at 95° C. for 40 minutes. In some embodiments, thereflective polarizer has a shrinkage in a range of 0.5 percent to 2.5percent, or in a range of 0.6 percent to 2 percent, along the block axisof the reflective polarizer when the reflective polarizer is heated at95° C. for 40 minutes.

Shrinkage of a multilayer reflective polarizer can be determinedaccording to the ASTM D2732-14 test standard. The shrinkage isdetermined for the reflective polarizer as a stand-alone film that isnot bonded or laminated to another substrate. For example, when theshrinkage of a reflective polarizer included in a polarizer stack isspecified, unless indicated differently, the shrinkage refers to theshrinkage of the reflective polarizer alone without other layers (e.g.,the absorbing polarizer) in the polarizer stack included.

FIG. 1 is a schematic cross-sectional view of polarizer stack 100 whichincludes an absorbing polarizer 110 and a reflective polarizer 120bonded together through adhesive layer 130. The absorbing polarizer 110includes an optically active layer 112 disposed between first and secondprotective layers 114 and 116. In some embodiments, one or bothprotective layers may be eliminated. In some embodiments, the opticallyactive layer 112 is an oriented polymer layer that may include adichroic dye or may include iodine. In some embodiments, the orientedpolymer is oriented polyvinyl alcohol. The optically active layer 112may have a thickness in the range of 1 micrometers, or 2 micrometers, or3 micrometers, or 5 micrometers to 50 micrometer or to 100 micrometers.For example, the optically active layer 112 may have a thickness in therange of 1 micrometers to 50 micrometers. The first and secondprotective layers 114 and 116 may be cellulose triacetate (TAC) orpoly(methyl methacrylate) (PMMA) layers, for example.

The reflective polarizer 120 includes first polymer layers 122alternating with second polymer layers 124. Four layers are shown inFIG. 1 for ease of illustration, but reflective polarizer 120 mayinclude tens, or hundreds, or even thousands of layers. The absorbingpolarizer 110 has a first block axis 118 and the reflective polarizerhas a second block axis 128. The first and second block axes 118 and 128are substantially parallel and in the illustrated embodiment areparallel to the y-axis, referring to the x-y-z coordinate system of FIG.1.

In the illustrated embodiment, the absorbing polarizer 110 and thereflective polarizer 120 are bonded together through an adhesive layer130. Adhesive layer 130 can be any suitable adhesive and may be anoptically clear or diffuse pressure sensitive adhesive. Suitableadhesives include Soken 1885 acrylic pressure sensitive adhesiveavailable from Soken Chemical and Engineering Co., Ltd., Tokyo, Japan,and 3M 8171 acrylic pressure sensitive adhesive available from 3MCompany, St. Paul, Minn. In alternate embodiments, the adhesive layer130 is omitted and the absorbing polarizer 110 and the reflectivepolarizer 120 are bonded together through the application of heat (forexample, using a heated roll laminator).

The reflective polarizer 120 has a shrinkage in a range of 0.4 percentto 3 percent along the second block axis 128 when the reflectivepolarizer 120 is heated at 95° C. for 40 minutes. In some embodiments,this shrinkage is at least 0.5 percent, or at least 0.6 percent. In someembodiments, this shrinkage is no more than 2.5 percent, or no more than2 percent. In some embodiments, this shrinkage is such that thereflective polarizer 120 is substantially free of micro-wrinkling (andin some embodiments, also substantially free of macro-wrinkling) whenthe polarizer stack 100 is heated at 95° C. for 100 hours or for 1000hours. In some embodiments, this shrinkage is such that the reflectivepolarizer 120 is substantially free of micro-wrinkling (and in someembodiments, also substantially free of macro-wrinkling) when thepolarizer stack 100 is heated at 100° C. for 100 hours or for 1000hours. In some embodiments, this shrinkage is 0.9 to 3 times a shrinkageof the absorbing polarizer 110 along the first block axis 118 when thereflective polarizer stack is heated at 95° C. for 40 minutes. Areflective polarizer may be said to be substantially free ofmicro-wrinkling, when no micro-wrinkling is visible when examined underan optical microscope at a magnification of 200 times.

In some embodiments, the polarizer stack includes an adhesive layerdisposed on the absorbing polarizer opposite the reflective polarizer.This adhesive layer may be included as an outer layer of the absorbingpolarizer (e.g., the adhesive layer of the Sanritz HLC2-5618S absorbingpolarizer (Sanritz Corp., Tokyo, Japan)) or may be a separate adhesivelayer applied to the absorbing polarizer (e.g., a pressure sensitiveadhesive such as 3M 8171 Optically Clear Adhesive (3M Company, St. PaulMinn.)). The adhesive layer allows to the polarizer stack to belaminated to a glass layer; for example, the glass layer in a liquidcrystal display panel facing the backlight (see FIG. 2). Unlessspecified differently, micro-wrinkling of a reflective polarizer in apolarizer stack is tested by maintaining the polarizer stack laminatedto a sheet of glass with the absorbing polarizer between the glass andthe reflective polarizer at a specified temperature for a specifiedtime, allowing the laminate of the glass and polarizer stack to cool toroom temperature, and then examining the reflective polarizer formicro-wrinkling.

Polarizer stack 100 is useful as a polarizer in a liquid crystal display(LCD). A liquid crystal display typically includes a display panelbetween crossed polarizers. Polarizer stack 100 can be used as either orboth of the crossed polarizers. In such display applications, thepolarizer stack 100 is typically oriented with absorbing polarizer 110facing the viewer and with the reflective polarizer 120 facing thebacklight.

FIG. 2 is a schematic cross-sectional view of display 240 including aliquid crystal layer 242 disposed between two glass layers 244 and 245,and a polarizer stack 200 adhered to the glass layer 244 with adhesivelayer 235. Display 240 further includes a backlight 247. It will beunderstood that additional layers, such as Brightness Enhancement Films(available from 3M Company, St. Paul, Minn.) can be disposed between thepolarizer stack 200 and the backlight 247. Polarizer stack 200 may beany of the polarizer stacks of the present description. For example,polarizer stack 200 may correspond to polarizer stack 100. Polarizerstack 200 includes an absorbing polarizer 210 and a reflective polarizer220 with the absorbing polarizer 210 facing the glass layer 244 and thereflective polarizer 220 facing the backlight 247. The absorbingpolarizer 210 and the reflective polarizer 220 may be laminated togetherwith an adhesive layer (not shown) or may be laminated together throughthe application of heat, for example. In some embodiments, thereflective polarizer 220 is substantially free of micro-wrinkling whenthe polarizer stack 200 laminated to a sheet of glass is heated at 95°C. for 100 hours or for 1000 hours. In some embodiments, the reflectivepolarizer 220 is substantially free of micro-wrinkling when thepolarizer stack 200 laminated to a sheet of glass is heated at 100° C.for 100 hours or for 1000 hours. In some embodiments, the reflectivepolarizer 220 is substantially free of both micro-wrinkling andmacro-wrinkling when the polarizer stack 200 laminated to a sheet ofglass is heated according to any of the temperature profiles describedabove. Adhesive layer 235 can be any suitable adhesive such as opticallyclear or diffuse pressure sensitive adhesives as described elsewhereherein.

EXAMPLES

Five variations of a multilayer reflective polarizer were made accordingto the method described in U.S. Pat. No. 6,827,886 (Neavin et al.). Thefilms had alternating birefringent and non-birefringent micro-layers;153 of these were birefringent and 152 were non-birefringent. Thebirefringent layers were produced from a 90%/10% (by moles) randomcopolymer of polyethylene naphthalate (PEN) and polyethyleneterephthalate (PET) at 42.3 wt % of the total extrusion rate. Thenon-birefringent layers were produced from a blend of two copolymers,with the first being 20.9 wt % of the total extrusion rate of a 90%/10%(by moles) copolymer of PEN and PET along with 28.9 wt % the totalextrusion rate of glycol modified PET (PETg, available from EastmanChemicals, Kingsport Tenn.). The skin layers on top and bottom of thefilm were produced from the same PETg as the non-birefringentmicrolayers; they were of equal thickness and represented 7.8 wt % ofthe total extrusion rate.

The films were each stretched on a standard tenter with a draw ratio ofabout six in the transverse direction and no stretching in the machinedirection. The five variations differed only according to the stretchconditions that were applied. Those conditions were: the temperature towhich the film was pre-heated, the temperature at which it wasstretched, the heat-set temperature in a first zone of the heat-setsection of the tenter, the heat-set temperature in a second zone of theheat-set section of the tenter, and the percent toe-in. Percent toe-inwas the amount the rails were moved inward during heat setting andsubsequent cooling step compared to the rail setting at the end ofstretching. Stretch conditions A, B, C, D and E are identified in Table1.

TABLE 1 Heat- Heat- Pre- set set heat Stretch Zone 1 Zone 2 Temp TempTemp Temp % Toe- Condition (° F.) (° F.) (° F.) (° F.) in A 308 284 291291 0.9% B 308 284 290 290 0 C 308 284 218 211 0 D 308 281 190 180 0 E303 273 182 180 0

Shrinkage was then measured for the five orientation conditions and forthe Sanritz HLC2-5618S Absorbing Polarizer (available from SanritzCorp., Tokyo, Japan). The shrinkage was measured using the ASTM D2732-14test standard. Shrinkage was measured in both pass and block axisdirections after exposure to 95 degrees C. for 40 minutes. Values arepresented in Table 2.

TABLE 2 Shrinkage at Shrinkage at 95° C. after 40 95° C. after 40minutes in minutes in Block state Pass state Condition directiondirection A 0.09% 0.29% B 0.26% 0.24% C 0.74% 0.68% D 1.46% 1.02% E2.65% 1.87% Sanritz 0.37% 0.24% HLC2- 5618S Absorbing Polarizer

Extended time shrinkage testing at 95 degrees C was also done for thefive multilayer film polarizer variations and the Sanritz absorbingpolarizer. Data for shrinkage in the block direction are shown in FIG.4, and shrinkage data for the pass direction are shown in FIG. 5.

The data in FIGS. 4-5 show that the shrinkage of the absorbing polarizerincreased at a higher rate than the two reflective polarizers (ConditionA and B reflective polarizers) produced with similar 4 minute shrinkagesfor both block-state and pass-state directions. Comparing FIGS. 4 and 5,it is also apparent that the shrinkage in the block-state direction forlong times was larger than the shrinkage in the pass-state direction forthe absorbing polarizer.

To test for micro-wrinkling, twenty-one samples of each of thereflective polarizers produced under Conditions A, B, C, D and E werechosen, and a piece approximately 1.25 in by 1.25 inch (3.2 cm by 3.2cm) was cut from each sample. These pieces were then adhered to thenon-adhesive side of similarly sized pieces of Sanritz HLC2-5618Sabsorbing polarizer using a pressure sensitive adhesive (8171 OpticallyClear Adhesive from 3M Company, St. Paul Minn.) with the block axis ofthe reflective polarizer parallel to the block axis of the absorbingpolarizer. Each construction was then laminated to glass using theadhesive of the absorbing polarizer to adhere the polarizer to the glassto create test samples. Three test samples of each construction werethen placed in one of six ovens. These ovens were set to 80, 85, 90, 95,100, and 105 degrees C. Three test samples were held at room temperature(RT). The test samples were held at their respective temperatures for1000 hours.

Micro-wrinkling was determined by examining the surface texture of thetest samples. When micro-wrinkling has appeared, it has been manifestedas objectionable haze in the film. Examined under a microscope at amagnification between 50× and 200×, micro-wrinkling has been observed asa permanent corrugation of the optical layers, and a rough exteriorlayer of the reflective polarizer could be observed.

A Perthometer M2 roughness measuring instrument produced by Mahr GmbH(Providence, R.I., USA) was used to characterize the surface roughnessin the block direction of the reflective polarizer in the test samplesused in micro-wrinkle testing. The results characterized by the surfaceroughness measure Ra (average of three samples) are shown in FIG. 6.These surface roughness results in combination with FIGS. 4-5 showedthat increased shrinkage in the reflective polarizer can reduce theseverity of micro-wrinkling.

The following is a list of exemplary embodiments of the presentdescription.

Embodiment 1 is a polarizer stack comprising an absorbing polarizerhaving a first block axis and a multilayer polymeric reflectivepolarizer having a second block axis substantially parallel to the firstblock axis, the absorbing polarizer and the reflective polarizer bondedtogether,

wherein the reflective polarizer, prior to being bonded to the absorbingpolarizer, has a shrinkage in a range of 0.4 percent to 3 percent alongthe second block axis when the reflective polarizer is heated at 95° C.for 40 minutes.

Embodiment 2 is the polarizer stack of Embodiment 1, wherein theabsorbing polarizer and the reflective polarizer are bonded togetherthrough an adhesive layer.

Embodiment 3 is the polarizer stack of Embodiment 1, wherein theshrinkage is in a range of 0.5 percent to 2.5 percent.

Embodiment 4 is the polarizer stack of Embodiment 1, wherein theshrinkage is in a range of 0.6 percent to 2 percent.

Embodiment 5 is the polarizer stack of Embodiment 1 further comprisingan adhesive layer disposed on the absorbing polarizer opposite thereflective polarizer, wherein the shrinkage is such that the reflectivepolarizer is substantially free of micro-wrinkling when the polarizerstack laminated to a glass sheet through the adhesive layer is heated at95° C. for 100 hours.

Embodiment 6 is the polarizer stack of Embodiment 1 further comprisingan adhesive layer disposed on the absorbing polarizer opposite thereflective polarizer, wherein the shrinkage is such that the reflectivepolarizer is substantially free of micro-wrinkling when the polarizerstack laminated to a glass sheet through the adhesive layer is heatedwith the glass sheet at 100° C. for 1000 hours.

Embodiment 7 is the polarizer stack of Embodiment 1, wherein theshrinkage of the reflective polarizer is 0.9 to 3 times a shrinkage ofthe absorbing polarizer along the first block axis when the polarizerstack is heated at 95° C. for 40 minutes.

Embodiment 8 is the polarizer stack of Embodiment 1, wherein theabsorbing polarizer comprises polyvinyl alcohol.

Embodiment 9 is the polarizer stack of Embodiment 8, wherein theabsorbing polarizer further comprises iodine.

Embodiment 10 is the polarizer stack of Embodiment 1, wherein theabsorbing polarizer comprises an optically active oriented polymer layerbonded to at least one protective layer.

Embodiment 11 is the polarizer stack of Embodiment 10, wherein theoptically active oriented polymer layer comprises polyvinyl alcohol andiodine.

Embodiment 12 is the polarizer stack of Embodiment 10, wherein theoptically active oriented polymer layer has a thickness in a range of 1to 50 micrometers.

Embodiment 13 is the polarizer stack of Embodiment 1, wherein thereflective polarizer comprises a plurality of alternating first andsecond polymer layers, at least one of the first and second polymerlayers being birefringent.

Embodiment 14 is the polarizer stack of Embodiment 1, wherein thereflective polarizer comprises a plurality of alternating first andsecond polymer layers, the first polymer layers having a firstrefractive index along the second block axis, the second polymer layershaving a second refractive index along the second block axis, the secondrefractive index lower than the first refractive index, the secondpolymer layers having a glass transition temperature less than 100° C.

Embodiment 15 is the polarizer stack of Embodiment 14, wherein the glasstransition temperature is less than 95° C.

Embodiment 16 is the polarizer stack of Embodiment 14, wherein the glasstransition temperature is less than 80° C.

Embodiment 17 is the polarizer stack of Embodiment 14, wherein the glasstransition temperature is less than 60° C.

Embodiment 18 is a display comprising a backlight, a glass layer and thepolarizer stack of claim 1, the polarizer stack further comprising anadhesive layer disposed on the absorbing polarizer opposite thereflective polarizer, the polarizer stack adhered to the glass layerthrough the adhesive layer, the polarizer stack disposed between theglass layer and the backlight.

Embodiment 19 is the display of Embodiment 18, wherein the reflectivepolarizer is substantially free of micro-wrinkling when the polarizerstack adhered to the glass layer is heated at 95° C. for 100 hours.

Embodiment 20 is the display of Embodiment 18, wherein the reflectivepolarizer is substantially free of micro-wrinkling when the polarizerstack adhered to the glass layer is heated at 95° C. for 1000 hours.

Embodiment 21 is the display of Embodiment 18, wherein the reflectivepolarizer is substantially free of micro-wrinkling when the polarizerstack adhered to the glass layer is heated at 100° C. for 1000 hours.

Descriptions for elements in figures should be understood to applyequally to corresponding elements in other figures, unless indicatedotherwise. Although specific embodiments have been illustrated anddescribed herein, it will be appreciated by those of ordinary skill inthe art that a variety of alternate and/or equivalent implementationscan be substituted for the specific embodiments shown and describedwithout departing from the scope of the present disclosure. Thisapplication is intended to cover any adaptations or variations of thespecific embodiments discussed herein. Therefore, it is intended thatthis disclosure be limited only by the claims and the equivalentsthereof.

What is claimed is:
 1. A polarizer stack comprising an absorbingpolarizer having a first block axis and a multilayer polymericreflective polarizer having a second block axis substantially parallelto the first block axis, the absorbing polarizer and the reflectivepolarizer bonded together, wherein the reflective polarizer issubstantially free of micro-wrinkling when the polarizer stack laminatedto a glass sheet through an adhesive layer disposed on the absorbingpolarizer opposite the reflective polarizer is heated with the glasssheet at 95° C. for 100 hours.
 2. The polarizer stack of claim 1,wherein the absorbing polarizer and the reflective polarizer are bondedtogether through an adhesive layer.
 3. The polarizer stack of claim 1,wherein the reflective polarizer is substantially free ofmicro-wrinkling when the polarizer stack laminated to the glass sheetthrough the adhesive layer is heated with the glass sheet at 100° C. for1000 hours.
 4. The polarizer stack of claim 1, wherein the reflectivepolarizer, prior to being bonded to the absorbing polarizer, has ashrinkage along the second block axis when the reflective polarizer isheated at 95° C. for 40 minutes, and wherein the absorbing polarizer hasa shrinkage along the first block axis when the polarizer stack isheated at 95° C. for 40 minutes, the shrinkage of the reflectivepolarizer being 0.9 to 3 times the shrinkage of the absorbing polarizer.5. The polarizer stack of claim 1, wherein the absorbing polarizercomprises polyvinyl alcohol.
 6. The polarizer stack of claim 5, whereinthe absorbing polarizer further comprises iodine.
 7. The polarizer stackof claim 1, wherein the absorbing polarizer comprises an opticallyactive oriented polymer layer bonded to at least one protective layer.8. The polarizer stack of claim 7, wherein the optically active orientedpolymer layer comprises polyvinyl alcohol and iodine.
 9. The polarizerstack of claim 7, wherein the optically active oriented polymer layerhas a thickness in a range of 1 to 50 micrometers.
 10. The polarizerstack of claim 1, wherein the reflective polarizer comprises a pluralityof alternating first and second polymer layers, at least one of thefirst and second polymer layers being birefringent.
 11. The polarizerstack of claim 1, wherein the reflective polarizer comprises a pluralityof alternating first and second polymer layers, the first polymer layershaving a first refractive index along the second block axis, the secondpolymer layers having a second refractive index along the second blockaxis, the second refractive index lower than the first refractive index,the second polymer layers having a glass transition temperature lessthan 100° C.
 12. The polarizer stack of claim 11, wherein the glasstransition temperature is less than 95° C.
 13. The polarizer stack ofclaim 11, wherein the glass transition temperature is less than 80° C.14. The polarizer stack of claim 11, wherein the glass transitiontemperature is less than 60° C.
 15. A display comprising a backlight, aglass layer and a polarizer stack, the polarizer stack comprising anabsorbing polarizer having a first block axis and a multilayer polymericreflective polarizer having a second block axis substantially parallelto the first block axis, the absorbing polarizer and the reflectivepolarizer bonded together, the polarizer stack further comprising anadhesive layer disposed on the absorbing polarizer opposite thereflective polarizer, the polarizer stack adhered to the glass layerthrough the adhesive layer, the polarizer stack disposed between theglass layer and the backlight, wherein the reflective polarizer issubstantially free of micro-wrinkling when the polarizer stack adheredto the glass layer is heated at 95° C. for 100 hours.
 16. The display ofclaim 15, wherein the reflective polarizer is substantially free ofmicro-wrinkling when the polarizer stack adhered to the glass layer isheated at 95° C. for 1000 hours.
 17. The display of claim 15, whereinthe reflective polarizer is substantially free of micro-wrinkling whenthe polarizer stack adhered to the glass layer is heated at 100° C. for1000 hours.